A syringe comprises an outer tube, a gasket inserted in the outer tube, and a pusher (plunger rod) connected to the gasket, and is used to discharge a liquid such as a chemical by pressing the pusher to slide the gasket in the outer tube toward the tip end thereof.
In this case, for discharging an accurate amount of the liquid, it is necessary to regulate the amount of movement of the gasket while looking at the graduations provided on the outer circumferential surface of the outer tube and to carefully operate the pusher.
In cases of the conventional syringes, however, the problem that the amount of the liquid discharged would be too large or too small is liable to be generated due to a misoperation (overpushing or insufficient pushing) of the pusher or misreading of the graduations.
As a syringe for solving such a problem, syringes in which the amount of movement of the pusher can be restricted have been proposed, for example, in Japanese Utility Model Publication No. Hei 2-15502 and Japanese Utility Model Laid-open No. Sho 62-119944.
In the syringe (syringe 10) described in Japanese Utility Model Publication No. Hei 2-15502, a stopper (regulation ring 56) is movable in the longitudinal direction by being rotated relative to a pusher (plunger 22). Upon an operation of pressing the pusher against an outer tube (hollow cylinder 2) in the condition where the stopper has been moved to a desired position of the pusher, the stopper comes into abutment on the base end of the outer tube, whereby the movement of the pusher is restricted. Incidentally, the symbols used here are the same as those described in the publication.
In the syringe described in the publication, however, a means for fixing the stopper relative to the pusher is not provided, and, therefore, the position of the stopper relative to the pusher may easily change, making it difficult to maintain the desired discharge amount of the liquid. In addition, since the stopper is moved by rotation relative to the pusher, the operation for moving the stopper is extremely intricate to perform.
On the other hand, in the syringe (syringe 1) described in Japanese Utility Model Laid-open No. Sho 62-119944, a stopper (stopper 3) is movable along the longitudinal direction of a pusher (piston 2). Upon an operation of pressing the pusher against an outer tube (cylinder 4) in the condition where the stopper has been moved to a desired position of the pusher, the stopper comes into abutment on the base end of the outer tube, whereby the movement of the pusher is restricted.
In the syringe described in the publication, however, the stopper is provided with a hole for passing the pusher therethrough, and the stopper is fixed relative to the pusher by the engagement of an engaging groove 5, formed in the outer circumferential surface of the pusher, with an edge portion of the hole. Therefore, a strong force is required for the operation of moving the stopper relative to the pusher. Incidentally, the symbols used here are the same as those described in the publication.
Accordingly, it is an object of the present invention to provide a syringe with which an accurate amount of a liquid can be discharged through a simple operation.